A typical computer system includes a connection structure for connecting multiple circuit boards of the computer system together (e.g., processor boards, memory boards, etc.) One such connection structure includes a backplane and a set of backplane connectors mounted to the backplane. For such a structure, the circuit boards include circuit board connectors which mate with the backplane connectors. That is, the backplane connectors and circuit board connectors typically include complementary sets of contacts, e.g., pins and pin-receiving contacts, which are configured to make effective electrical contact with each other when the backplane connectors and circuit board connectors mate. The distance from when such pins initially make electrical contact with their complementary pin-receiving contacts (the point of contact) and when the pins become fully seated within the pin-receiving contacts is commonly referred to as xe2x80x9cpin wipexe2x80x9d.
Installation of a circuit board into a computer system typically involves a user sliding the circuit board into an opening of a card cage of the connection structure. The backplane typically resides at the rear end of the card cage (or in the middle of the card cage if the card cage is configured to receive circuit boards through both ends). As the circuit board slides within the card cage, circuit board connectors along the edge of the circuit board eventually engage backplane connectors mounted to the backplane at the rear of the card cage. After the circuit board connectors make electrical contact with the backplane connectors, the user continues to slide the circuit board further into the card cage until the circuit board moves into a fully seated position within the card cage (e.g., until the circuit board connectors reach an interference fit with the backplane connectors, or until the user has fully closed levers of the card cage or the circuit board, etc.). The user can repeat this installation process for other circuit boards as well.
Often, the circuit board or card cage includes one or more levers which the user operates when moving the circuit board into its fully seated the position. Such levers assist the user in properly positioning the circuit board within the card cage such that the circuit board connectors correctly align with the backplane connectors. Additionally, the levers enable the user to evenly provide the proper amount of insertion force so that the contacts (e.g., pin-receiving contacts) of the circuit board connectors properly mate with the contacts (e.g., pins) of the backplane connectors.
Low amounts of pin wipe (the available region for electrical contact between circuit board contacts and backplane contacts) may result in poor electrical connectivity between the circuit boards and the backplane. In some situations, low amounts of pin wipe can cause intermittent breaks in electrical pathways between one or more circuit boards and the backplane resulting in computer system failures or errors.
There can be many causes for low amounts of pin wipe. For example, one cause can be a poor connector design (e.g., the pins, the pin-receiving contacts or both can be too short to adequately provide sufficient electrical connectivity). Another cause can be poor manufacturing of connection components (e.g., the connector components may exceed their design tolerances thus preventing the connectors from providing an intended amount of pin wipe). In low pin wipe conditions, movement of the computer system (e.g., due to vibrations of one or more cooling fans) tends to exacerbate poor electrical connectivity situations often resulting in intermittent failures making the cause of the failure, i.e., insufficient pin wipe, difficult to identify.
One approach to identifying an insufficient pin wipe situation is to dissemble the connection structure and perform a visual inspection. In particular, a human inspector first removes a circuit board from the computer system in order to access the circuit board connectors, and extracts the backplane (and mounted backplane connectors) from the computer system in order to clearly view the backplane connectors. The inspector then cross-sectionally cuts (e.g., using a high-speed precision saw) through the circuit board connectors and the backplane connectors. Next, the inspector moves the circuit board toward the backplane in order to engage the remaining portion of the circuit board connectors with the remaining portion of the backplane connectors. The inspector provides such movement in an attempt to simulate installation of the circuit board within the computer system. While the inspector engages the connectors, the inspector measures the distance between connectors at the point of contact between connector contacts, and when the connectors reach the fully seated position, in order to determine the actual amount of pin wipe provided by the connectors.
Unfortunately, there are deficiencies to measuring pin wipe using the disassembly approach involving extracting of the backplane from the card cage, and cutting of the circuit board and backplane connectors. For example, this approach requires the labor-intensive task of removing the backplane from the card cage (e.g., removing screws, nuts, bolts, etc.). Furthermore, this approach requires cutting through the circuit board and backplane connectors to expose the circuit board and backplane contacts which typically requires a precision saw in order to leave portions of the connectors intact. Additionally, as the inspector moves the circuit board toward the backplane to simulate circuit board installation, the inspector must make a proper visual determination of when the circuit board connectors make electrical contact with the backplane connectors, and such visual determinations can often be inaccurate. Moreover, there is no guarantee that the inspector has accurately simulated installation of the circuit board within the computer system. For example, the circuit board connectors may normally reach a fully seated position relative within the backplane connectors when levers assisting circuit board installation reach a closed position, but the inspector may attempt to measure pin wipe by forcing the circuit board connectors further into the backplane connectors until the circuit board connectors reach an interference fit with the backplane connectors. Such a measurement may overstate the amount of actual pin wipe provided in similar configurations in the field which avoid such further insertion of the circuit boards once the levers have reached a fully closed position.
In contrast to the conventional disassembly approach, the invention is directed to techniques for obtaining a connection characteristic (e.g., pin wipe) of a connection assembly having a first set of contacts (e.g., pin-receiving contacts of circuit board connectors) and a second set of contacts (e.g., pins of backplane connectors) using less destructive approaches. In particular, the invention does not rely on disassembling a backplane from a card cage and cutting connectors. Rather, in one arrangement, the invention uses a test structure in place of a normal operating circuit board. The test structure includes a support member (e.g., circuit board material) that supports the first set of contacts, and that is capable of moving relative to the second set of contacts. The test structure further includes a detection circuit, coupled to the support member, that detects an electrical event resulting from movement of the first set of contacts relative to the second set of contacts (e.g., making electrical contact between the first and second sets of contacts). The test structure also includes a measuring device, coupled to the support member, that identifies position coordinates resulting from movement of the first set of contacts relative to the second set of contacts. The measuring device enables a user to identify (i) a first position coordinate in response to the electrical event resulting from movement of the first set of contacts relative to the second set of contacts, and (ii) a second position coordinate in response to a mechanical event resulting from movement of the first set of contacts relative to the second set of contacts (e.g., the first set of contacts reaching a fully seated position relative to the second set of contacts). A difference between the first and second position coordinates provides the connection characteristic of the connection assembly.
The use of the invention alleviates the need to disassemble a backplane from a card cage and the need to cut connectors as is done for each test in the conventional disassembly approach for measuring pin wipe. The test structure used by the invention is reusable and portable, and can be used to measure connection characteristics of products in a manufacturing assembly line, or out in the field (e.g., at customer sites).
In one arrangement, the detection circuit of the test structure is configured to detect, as the electrical event, formation of a parallel circuits through the first and second sets of contacts. Accordingly, if the positions of contacts which form the parallel circuits are distributed along an edge of the test structure, the formation of the parallel circuits provides an indication to the user that the first set of contacts is evenly aligned (i.e., not substantially crooked) with the second set of contacts at the point of contact between the first and second sets of contacts.
In one arrangement, the first set of contacts belong to a first set of connectors, and the second set of contacts belong to a second set of connectors. In this arrangement, the measuring device of the test structure is configured to output a measurement value, as the second position coordinate, in response to detection of movement of the first set of connectors into a fully seated position relative to the second set of connectors, as the mechanical event. Accordingly, the user can read the measurement value of the measuring device when the first set of connectors are fully seated relative to the second set of connectors, and subsequently determine the connection characteristic based on that measurement value.
In one arrangement, the connection assembly further includes a card cage having a backplane. In this arrangement, the first set of contacts belong to a first set of connectors which is mounted to the support member, and the second set of contacts belong to a second set of connectors which is mounted to the backplane. The support member of the test structure is configured to move relative to the backplane within the card cage such that the first set of contacts move relative to the second set of contacts. As such, the user can use the invention to measure position coordinates while the backplane resides within the card cage, and the user does not need to extract the backplane from the card cage.
In one arrangement, the measuring device of the test structure is configured to provide a first measurement as the first position coordinate, and a second measurement as the second position coordinate. In this arrangement, the first and second measurements indicate locations along an axis. Accordingly, the difference between the first and second position coordinates is a straight line distance (i.e., pin wipe) along that axis.
The features of the invention, as described above, may be employed in systems, devices and methods for testing computer systems (e.g., data storage systems) and other computer-related components such as those manufactured by EMC Corporation of Hopkinton, Mass.